Human Hepatocyte Growth Factor (HGF) is a multifunctional heterodimeric polypeptide produced by mesenchymal cells. HGF has been shown to stimulate angiogenesis, morphogenesis and motogenesis, as well as the growth and scattering of various cell types (Bussolino et al., J. Cell. Biol. 119: 629, 1992; Zarnegar and Michalopoulos, J. Cell. Biol. 129:1177, 1995; Matsumoto et al., Ciba. Found. Symp. 212:198, 1997; Birchmeier and Gherardi, Trends Cell. Biol. 8:404, 1998; Xin et al. Am. J. Pathol. 158:1111, 2001). The pleiotropic activities of HGF are mediated through its receptor, a transmembrane tyrosine kinase encoded by the proto-oncogene cMet. In addition to regulating a variety of normal cellular functions, HGF and its receptor c-Met have been shown to be involved in the initiation, invasion and metastasis of tumors (Jeffers et al., J. Mol. Med. 74:505, 1996; Comoglio and Trusolino, J. Clin. Invest. 109:857, 2002). HGF/cMet are coexpressed, often over-expressed, on various human solid tumors including tumors derived from lung, colon, rectum, stomach, kidney, ovary, skin, multiple myeloma and thyroid tissue (Prat et al., Int. J. Cancer 49:323, 1991; Chan et al., Oncogene 2:593, 1988; Weidner et al., Am. J. Respir. Cell. Mol. Biol. 8:229, 1993; Derksen et al., Blood 99:1405, 2002). HGF acts as an autocrine (Rong et al., Proc. Natl. Acad. Sci. USA 91:4731, 1994; Koochekpour et al., Cancer Res. 57:5391, 1997) and paracrine growth factor (Weidner et al., Am. J. Respir. Cell. Mol. Biol. 8:229, 1993) and anti-apoptotic regulator (Gao et al., J. Biol. Chem. 276:47257, 2001) for these tumors.
HGF is a 102 kDa protein with sequence and structural similarity to plasminogen and other enzymes of blood coagulation (Nakamura et al., Nature 342:440, 1989; Weidner et al., Am. J. Respir. Cell. Mol. Biol. 8:229, 1993). Human HGF is synthesized as a 728 amino acid precursor (preproHGF), which undergoes intracellular cleavage to an inactive, single chain form (proHGF) (Nakamura et al., Nature 342:440, 1989; Rosen et al., J. Cell. Biol. 127:1783, 1994). Upon extracellular secretion, proHGF is cleaved to yield the biologically active disulfide-linked heterodimeric molecule composed of an α-subunit and β-subunit (Nakamura et al., Nature 342:440, 1989; Naldini et al., EMBO J. 11:4825, 1992). The α-subunit contains 440 residues (69 kDa with glycosylation), consisting of the N-terminal hairpin domain and four kringle domains. The β-subunit contains 234 residues (34 kDa) and has a serine protease-like domain, which lacks proteolytic activity. HGF has two unique cell specific binding sites: a high affinity (Kd=2×10−10 M) binding site for the cMet receptor and a low affinity (Kd=10−9 M) binding site for heparin sulfate proteoglycans (HSPG), which are present on the cell surface and extracellular matrix (Naldini et al., Oncogene 6:501, 1991; Bardelli et al., J. Biotechnol. 37:109, 1994; Sakata et al., J. Biol. Chem., 272:9457, 1997).
The cMet receptor is a member of the class IV protein tyrosine kinase receptor family. The full length cMet gene was cloned and identified as the cMet proto-oncogene (Cooper et al., Nature 311:29, 1984; Park et al., Proc. Natl. Acad. Sci. USA 84:6379, 1987). NK2 (a protein encompassing the N-terminus and first two kringle domains of the α-subunit) is sufficient for binding to cMet and activation of the signal cascade for motility, however the full length protein is required for the mitogenic response (Weidner et al., Am. J. Respir. Cell. Mol. Biol. 8:229, 1993). HSPG binds to HGF by interacting with the N terminus of HGF.
HGF/cMet have been reported to play important roles in several aspects of cancer development such as tumor initiation, invasion, metastasis, regulation of apoptosis and angiogenesis. Several different approaches have been investigated to obtain an effective antagonistic molecule: truncated HGF proteins such as NK1 (N terminal domain plus kringle domain 1; Lokker et al., J. Biol. Chem. 268:17145, 1993), NK2 (N terminal domain plus kringle domains 1 and 2; Chan et al., Science 254:1382, 1991) and NK4 (N-terminal domain plus four kringle domains; Kuba et al., Cancer Res. 60:6737, 2000), anti-cMet mAbs (Dodge, Master's Thesis, San Francisco State University, 1998) and anti-HGF mAbs (Cao et al., Proc. Natl. Acad. Sci. USA 98:7443, 2001, which is incorporated herein by reference).
NK1 and NK2 can compete effectively with the binding of HGF to its receptor, but have been reported to have partial agonistic activities in vitro (Cioce et al., J. Biol. Chem. 271:13110, 1996; Schwall et al., J. Cell Biol. 133:709, 1996), rather than purely antagonist activities as desired. More recently, Kuba et al., Cancer Res. 60:6737, 2000, reported that NK4 could partially inhibit the primary growth and metastasis of murine lung tumor LLC in a nude mouse model by continuous infusion of NK4. However, the fact that NK4 had to be administered continuously to obtain a partial growth inhibition of primary tumors indicates a potentially short half-life of the NK4 molecule and/or lack of potency.
Cao et al., Proc. Natl. Acad. Sci. USA 98:7443, 2001, reported that the administration of a cocktail of three anti-HGF mAbs, which were selected based upon their ability to inhibit the scattering activity of HGF in vitro, were able to inhibit the growth of human tumors in the xenograft nude mouse model. They postulated that three mAbs recognizing three different binding sites on HGF were required to inhibit the bioactivities of HGF in vivo: two mAbs inhibited the binding of HGF to cMet and one mAb inhibited the binding of HGF to heparin.
Recently, human mAbs that individually bind and neutralize HGF developed using transgenic mouse technology have been reported (Burgess et al., WO 2005/017107A2 and Burgess et al., Cancer Res 66:1721, 2006, each of which is herein incorporated by reference for all purposes). However, of these at least the 2.12.1 mAb, which was apparently the most potent in tumor xenograft models, nonetheless did not inhibit angiogenesis. A mouse mAb L2G7 has been developed that neutralizes all tested biological activities of HGF including angiogenesis (patent application U.S. Ser. No. 10/917,915 filed Aug. 13, 2004, and Kim et al. Clin Cancer Res 12:1292, 2006, each of which is herein incorporated by reference for all purposes).
Thus, there is a need for a humanized monoclonal antibody that blocks biological activity of HGF in vitro and in vivo. The present invention fulfills this and other needs.